Drag Specialties Spark Plug Wire Set For Harley Drag Specialties spark plug wire set uses an 8.8 mm construction with silicone in the jacket, insulation, and core. It is designed to withstand high temperatures and serves as a reliable replacement for worn ignition components on a Harley. Features: Constructed with silicone throughout the jacket, insulation, and core for high-temperature resistance 8.8 mm Made in the USA